/// <summary>
/// Evaluates a <see cref="Board" />.
/// </summary>
/// <param name="board">The <see cref="Board" /> to evaluate.</param>
/// <returns>A numeric value indicating the strenght of the position for the current player.</returns>
public static int Evaluate(Board board)
{
var evaluation = 0;
if (board.Winner != Players.None)
{
if (board.Winner == board.Current)
{
evaluation = int.MaxValue;
}
else
{
evaluation = int.MinValue;
}
}
else
{
var visitedLines = new List <Line>();
for (var x = 0; x < Constants.Dimension; x++)
{
for (var y = 0; y < Constants.Dimension; y++)
{
for (var z = 0; z < Constants.Dimension; z++)
{
var position = new Coordinate(x, y, z);
if (board.GetPlayer(position) != Players.None)
{
foreach (var line in new ValidLineCollection(position))
{
if (!visitedLines.Contains(line))
{
evaluation += BoardEvaluator.Evaluate(line, board);
visitedLines.Add(line);
}
}
}
}
}
}
}
return(evaluation);
}
private static int Evaluate(Line line, Board board)
{
var evaluation = 0;
var last = Players.None;
var current = board.Current;
var continuationFactor = 1;
foreach (var position in line)
{
var atPosition = board.GetPlayer(position);
if (atPosition != Players.None)
{
if (atPosition == last)
{
evaluation += continuationFactor * (atPosition == current ? 1 : -1);
continuationFactor += BoardEvaluator.UpdateContinuation(continuationFactor);
}
else
{
continuationFactor = 1;
evaluation += continuationFactor * (atPosition == current ? 1 : -1);
}
}
last = atPosition;
}
var start = board.GetPlayer(line.Start);
if (start != Players.None && start == board.GetPlayer(line.End))
{
evaluation += (current == start ? 2 : -2);
}
return(evaluation);
}
private int Evaluate(Board board)
{
this.Evaluations++;
return(BoardEvaluator.Evaluate(board));
}